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Subject: search.filters.subject.Stator winding

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    The Study of Partial Discharge of a Decommissioned 11kV Rotating Machine
    (2024-01-01)
    Waiwicha, Supisara
    ;
    Monkolsatitpong, Suriya
    ;
    Inwanna, Woranan
    ;
    Vanijkirati, Parada
    ;
    Jeenmuang, Siwakorn
    Over time the insulation system of the stator winding in machinery will gradually lose electrical and mechanical strength due to factors such as thermal, electrical, ambient, and mechanical stressors. At a certain point, the material will deteriorate significantly to the extent that the insulation breaks down or cracks under normal operating voltages, due to transient electrical or mechanical situations. This paper presents a study of the stator winding insulation system of a decommissioned 11kV motor with the removed rotor, using offline PD measurement. The measurement results revealed PD signals in all three phases. The PRPD patterns indicate internal delamination discharge and discharge at stress control coating(S/C) and stress control grading which is occurring simultaneously. When the test voltage is increased to a certain point, the electric field stress in the stress control grading area becomes high enough to cause a gap-type discharge pattern, occurring between the press finger and the stress control grading area. Visual inspections also revealed spark discharge.
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    Additional parameters for elucidation of the dielectric behavior of stator winding in high voltage motors
    (2022-11-01)
    Pattanadech, Norasage
    ;
    Phloymuk, Natthawut
    ;
    Nimsanong, Pethai
    ;
    Srinangyam, Chissanupong
    ;
    Jeenmuang, Siwakorn
    This paper proposes additional parameters for describing the dielectric behaviors of the stator winding in high voltage motors used in coal power plants. The on-site MV induction motors with indirect air-cooling rated 6.6 kV, 260 to 3091 kW, were investigated. These motors were installed in different parts of the plants and operated under different conditions. Therefore, the stator winding conditions of such motors were different. The integral insulation conditions of stator winding were examined by analysis of the dielectric response. Whereas the local insulation conditions of the stator winding, the so-called weak spot condition, were examined by analysis of the off-line PD test results. To deeply understand the dielectric behavior of such stator windings, a proposed simplified equivalent circuit for modeling the insulation system of the stator winding was introduced and constructed, which aimed to distinguish the dielectric behavior into conductivity, polarization, and ionization mechanisms. The additionally parameters, i.e., the minor capacitance (C<inf>i</inf>), the minor resistance (R<inf>i</inf>), the dc resistance (R<inf>dc</inf>), the minor capacitance at defect site (C<inf>PD</inf>), the conductivity loss factor (Tan δ<inf>σ</inf>), and the polarization loss factor (Tan δ<inf>pol</inf>) were estimated and proposed. It can be concluded that the proposed additional parameters are a valuable tool for assessing the insulation condition, which reduces the ambiguity in the interpretation of the insulation test results and is suitable for monitoring insulation conditions over the service life of the high voltage motors.
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    Polarization and depolarization current characteristics of thermally stressed stator bars
    (2019-07-01)
    Pattanadech, N.
    ;
    Srichuen, N.
    ;
    Wang, C.
    ;
    Kaewdee, N.
    ;
    Poungpat, T.
    Polarization and depolarization current (PDC) measurement was used in this research to investigate the insulation integrity of stator bars. This method is non-destructive testing. This paper presents the PDC analysis of thermally stressed stator bars divided into two main groups. The first group was heated at 100^{\circ}C and the second group was heated at 130 ^{\circ}C for 36 hours. After 12, 24 and 36 hours of heating process, PDC measurement of each test specimen was performed. PDC test results including capacitance ratio and dielectric dissipation factor were analyzed and reported.